Communications systems, including wireless communications systems, typically communicate through non-ideal channels. For example, conditions such as electromagnetic interference, signal degradation, phase delays, component mismatches, fading, and other circuit and/or environmental non-idealities may attenuate or distort a communications signal or may otherwise interfere with the communications capabilities of the system. Moreover, compensating for these and other channel non-idealities is complicated by the dynamic variation that is often associated with many of these factors.
Communications systems may employ link adaptation technologies to adjust communications parameters based on variations of communications channel condition values. For example, link adaptation may be employed in conjunction with many wired and/or wireless communications systems or standards such as Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), Enhanced Data GSM Environment (EDGE), Digital Subscriber Line (DSL), Data Over Cable Service Interface Specification (DOCSIS), proprietary systems or protocols, and/or the like.
In these and other systems, link adaptation may be employed to adjust parameters such as transmitter output power, receiver input sensitivity, strength of channel coding, symbol rate, allocated spectrum, modulation type, and/or the like in response to channel condition values. In one example, link adaptation is employed to increase the strength of channel coding when communicating through a relatively noisy channel and to decrease the strength of channel coding when communicating through a relatively noise free channel. In this example, the strength of the channel coding may be adjusted to balance the transmission rate of payload data with the ability of the receiver to recover the payload data from the non-ideal channel. In such a manner, link adaptation may be employed to improve the throughput of payload data over a wide range of channel conditions.
Additional details regarding link adaptation may be as described by the 3rd Generation Partnership Project (3GPP) technical specification (TS), which is hereby incorporated by reference. For example, TS 25.212, TS 25.308, and TS 25.321 provide additional details regarding link adaptation.